(Reuters) - The European Commission said on Friday that an international deal to curb Iran's nuclear program struck in 2015 was working and all sides should stick to their commitments.

U.S. President Donald Trump is expected to announce soon that he will decertify the landmark agreement, a senior administration official said on Thursday. Trump faces an Oct. 15 deadline for certifying that Iran is complying with the deal's terms.

"We are following very closely all the developments on the deal... reminding that it is a non-proliferation deal, which has been endorsed by the UN Security Council, that it's working, delivering as it has been verified eight times by the international agency for atomic energy," a Commission spokeswoman told a news conference in Brussels.

"It is a durable, long-term solution to the Iranian nuclear issue which gives all sides the necessary assurances and we expect all sides to stick to their commitments under the deal," she added.